Package for the storage and transportation of radioactive substances containing both neutron and gamma radiation absorbing material

ABSTRACT

The package has a composite wall comprising from inside to outside, a inner shell surrounding the useful cavity, a layer of dense material for protection against gamma radiations and an outer shell. A layer of neutron-absorbing material is arranged against the other surface of the outer shell, heat conducting elements, such as fins or pins, being fixed against the outer shell and projecting at the surface of the layer.

QR 3727mm a HEMM [United @mt [11] 372mm Bllum [45] Apr. 10, 1973 PACKAGE FQR AND [58] Field of Search ..250/108 R, 108 WS TRANSPORTATKON 01F RADHOACTHVE SUBSTANCES coNTA NG now [561 References CM NEUTRON AND GAMMA RADIATION UNITED STATES PATENTS 1 #1 ENG MATERIAL 3,111,586 11/1963 Rogers ..250/108 R [75] Inventor: lPaul Blum, Saint-Nom-la-Breteche, 3,414,727 12/1968 Bonilla ..250/ 108 R France 3,005,105 10/1961 Lusk t ..250/l08 R 3,056,028 9/1962 Mattingly ..250/108 WS [73] Assrgnee: Transnucleaire, Suciete Pour les Transports de LHudustrie Nucleaire Primary Examiner-Archie R. Borchelt yams France Att0meyLarson, Taylor and Hinds [22] Filed: Aug. 13, 1970 [57] ABSTRACT [21] Appl. No.: 63,529

The package has a composite wall comprising from mside to outside, a inner shell surrounding the useful [30] Foreign Application Priority Data cavity, a layer of dense material for protection against Aug. 13, 1969 France ..6927937 gal-mm radlanfms and i (.mter Shell A of neutron-absorbing material 18 arranged against the Jan. 14, 1970 France ..700l265 14 other surface of the outer shell, heat conducting ele- May 8,1970 France ..70l69 ments, such as fins or pins being fixed against the outer shell and projecting at the surface of the layer. [52] US. Cl. .250/108 1R, 250/108 WS [51] lint. Cl ..G21f 1/02, G2lf 5/00 13 Claims, 11 Drawing Figures PATENTH] APR] 01975 SHEET 1 BF 6 PATENTEDAPR 1 mm 3.727. 060

SHEET 5 [1P6 PATENTEB 1 01815 3,727, 060

SHEET 8 OF 6 PACKAGE FOR THE STORAGE AND TRANSPGRTATION OF RADIOACTIVE SUBSTANCES CONTAINING BOTH NEUTRON AND GAMMA RADIATION ABSORBING MATERIAL The invention relates to a package for the transportation and storage of radioactive materials of the type which includes a composite wall comprising an inner shell, a layer or core of dense material such as lead and an outer shell, the inner and outer shells being generally constructed of steel.

It is a particular object of'the invention to render such the abovesaid packages that they provide an efficient barrier to neutrons emitted by the radioactive materials whilst enabling the dissipation of the heat produced by the latter.

The package according to the invention is characterised by the fact that it comprises a layer of neutron absorbent material in which are buried, at least partially, heat conducting elements.

The invention will be better understood with the aid of the supplementary description which follows, as well as of the accompanying drawings, which description and drawings relate to several embodiments of packages according to the invenion, given purely by way of illustrative but non limiting example.

In the drawings,

FIG. 1 shows in sectional perspective, a portion of one embodiment of the package according to the invention;

FIG. 2 is a plan view of a portion of the outer surface of the embodiment of FIG. 1;

FIG. 3 is a cross-section of a second embodiment of a package according to the invention;

FIGS. 4 and 5 show in perspective two variations of the above-mentioned first embodiment;

FIGS. 6 and 7 show on a larger'scale two embodiments of a portion of the package according to FIG. 3;

FIG. 8 shows in cross-section a variation of the embodiment of FIG. 3;

FIG. 9 is a view in elevation with partial section of the embodiment of FIG. 3; and lastly FIGS. 10 and 11 show, in axial section, two other em-- bodiments of the package according to the invention.

According to the principal feature of the invention, a package for radioactive materials and of which the wall comprises, from the cavity towards the outside, an inner shell 1, a layer 2 of dense material such as lead for the protection against the gamma radiations and an outer shell 3, the shells I and 3 being generally constructed of steel comprises a layer 4 of a neutraon abosrbing material in which are buried at least partially conducting elements.

In a first preferred embodiment the layer 4 is arranged against the outer surface of the shell 3 and the heat conducting elements, of the type of fins or pins, are fixed against the outer surface of the shell 3.

More particularly in the embodiment of FIG. 1, the heat conducting elements are obtained from metallic blades 6, fixed by welding at one of their edges on the shell e parallel to the axis of the package, that is to say along a generator X X The blades 6 include on their free edge a succession of fins 7 folded back through one of their sides to a blade support and having undergone, close to this side, a twisting such that their flat portions are situated in successive planes substantially parallel between themselves and perpendicular to the axis of the package, that is to say to X X To construct the abovesaid fins 7, there are formed on one of the edges of the blades 6, before the fixing of the latter on the package, incisions perpendicular to the said edge and stopping at a short distance d from the other edge, which give successive teeth situated in extension of one another.

The said blades are then welded on the package.

In FIG. 1 there are shown in mixed lines several of the successive teeth concerned and at 7a the incisions separating them.

It suffices then to make each of the teeth undergo successively a twisting of around an axis perpendicular to the axis of the package to arrange that each of the said teeth has a flat portion substantially parallel to the flatportions of the neighbouring teeth and perpendicular to the axis of the package, thus forming the fins 7.

At the time of welding the blades 6 on the package, it is arranged for the incisions borne by a 'given blade not to be placed facing the incisions of the neighbouring baldes.

An advantageous arrangement is that which results from FIG. 2 and according to which the fins 7 are arranged in quincunx.

As regards the constituent metal of the blades 6, it is selected advantageously in the group comprising steel, copper, aluminium and alloys based on these metals.

There are cases where the package is transported in inclined manner. To have an optimum cooling effect, there is then conferred on the fins an inclination such, with respect to the axis of the package, that the flat portions of the said fins are situated in a vertical plane when the package is placed in the inclined position of transportation.

The fins which have just been described combine the efficiency of known fins in the form of a crown surrounding the package and the facility of positioning of the fins also known constituted by single baldes, welded on the shell 3 parallel to the axis X Y, and whose efficiency of cooling leaves something to be desired.

It is also possible, to constitute the heat conducting elements by welded pins, known in themselves.

In a second advantageous embodiment, the layer 4 is arranged inside the shell 3 and the heat conducting elements, of which at least one end is free, are buried in the said layer 4.

More particularly according to the embodiment of FIG. 3, the heat conducting elements, metallic as in the preceding embodiment (certain at least being preferably of steel and serving then as centering elements) have a section especially in a U" or in the I," said elements which have been denoted by 8, being arranged so that the horizontal bar of the U or the vertical limb of the I are oriented radially.

The elements 8 can also be arranged in the form of a T or of an L, the vertical limb of the T or of the L being then fixed on the layer 2, the horzontal bar, parallel to the outer shell 3, thus increasing the heat exchange of the surface. Of course, the reverse atrangement is possible.

It is also possible to give to the portion of the heat conducting element which is arranged across the layer 4 a direction inclined with respect to the radius.

In the one and the other preceding embodiments, the neutron absorbing material is a material rich in hydrogen and, possibly, in boron.

To form this material, recourse may be had to synthetic and/or mineral substances.

As regards the synthetic sbstances rich in hydrogen recourse may be had for example to polythene and similar substances.

As regards to the minerals rich in hydrogen and boron, there may be used for example colemanite (3 E ZCaO, H O), pandermite (6 B 0 5 CaO, 6H O) or again boric acid H hd 3 B0 There may also be used frits of boron glass. Similarly, it is possible to use boron concretes, mixtures of plaster, polythene and boric acid, wood advantageously injected of boric acid or agglomerates of wood with or without boron.

When the layer 4 is arranged between the outer surface of the shell 3, there is advantageously used a material capable of being cast to which there can be added a plasticiser such as bentonite to improve the smoothness and impermeability. It is however possible also to use hoops 4a of wood or similar hydrogenated material, advantageously injected by boron, as shown in FIG. 4 in which there is shown two hoops 4a assembled by suitable means such as bolts 4b and arranged between the annular fins 14. In another embodiment, shown in FIG. 5, there are provided blades 6 forming longitudinal fins between which are fixed wooden elements 4c or of other hydrogenated material, parallel to the axis X,Y

When the layer 4 is arranged against the inner surface of the shell 3, recourse may be had to plates formed of a material rich in hydrogen and/or boron, which plates are deonted by the reference 9 and which are housed, as seen in FIG. 6, in the space located between the branches of the U-form elements, the said plates as well as the elements 8 being then connected to one another as well as to the layer 2 and to the outer shell 3 by means of a binding. This binding can however be of the type which set by hydration and which can retain free water. In FIG. 6, this binding is denoted by 10.

It is also possible to have recourse, for constituting the binding, to plaster and to resins of the polyesther or epoxy type filled or not with boron based products.

In a variation illustrated in FIG. 7, the material 4 comprises, as in the case of the embodiment of FIG. 8, a binding which is designated by 10 and in which are buried, on one hand, the cooling elements 8 and, on the other hand, particles 11 of a material rich in atoms of hydrogen, as well as, if necessary, atoms of boron.

To establish ideas, it is indicated that the constituent material of the plates 9 and/or particles 11 can be polyethylene or a wood based agglomerate composition.

As regards the binding 10, recourse may be had to an aluminous cement comprising from 35 to 40 percent alumina, from 35 to 40% of CaO, from 10 to 15% of Fe O from 2 to 8% of FeO, from 2 to 7% of SiO from 0 to 3% of TiO and from 0 to 3 percent of various substances.

In other cases, the binder is constituted by plaster or resins of the epoxy or polyester type.

In certain cases, the package according to the invention comprises, as seen in FIG. 3 and FIG. 8, a plurality of cavities C each bounded by an inner shell 1 advantageously constructed of stainless steel, these cavities being distributed around the axis of the package designated by XY, and spaces comprised between the various inner shells 1 being at least partially filled by a metal lighter than lead and denoted by 12. For reasons of ease of manufacture, the metal 12, which is constituted advantageously by aluminium, cast iron or steel, forms elements which are buried in the midst of the constituent material of the layer 2, as seen in FIG. 3.

It is also possible, as seen in FIG. 8, to arrange that the spaces comprised between the various cavities are constituted by the constituent steel itself of the inner shell.

It is again possible, even in the case of a single cavity, to provide thickenings 13 of the inner shell on the flat portions of the latter, as seen in FIG. 8, which enables a gain in weight to be recorded following the elimination of the lead at the places concerned and to increas the heat capacity.

Due to the presence of the elements 12 constituted by the metal lighter than lead, there are improved, on the one hand, the possibilities of thermal exchanges and, on the other hand, the possibilities of neutron absorption, the metals concerned being from this point of view superior to lead.

Finally, the presence of elements of metal lighter than lead enables the improvement of the control of nuclear interaction between the fuel elements contained in the difierent cavities C.

The outer contour of the layer 2 being capable of taking various shapes, for example as seen in FIG. 8, there can be conferred on the layer of material 4 a varying thickness in order that the outer shell can be of simple shape, for example that of a cylinder of revolution. To do this, according to the invention, recourse is had, as visible in FIG. 8, to elements 8 of variable sizes.

Always according to the invention, the thickness of the layer of material 4 varies in the direction of the axis of the package.

This characteristic appears in FIG. 9, which represents a view in elevation of a package according to the invention including a tear away which shows the inside of the package.

As visible in this Figure, the thickness of the layer of material 4, which is least at mid-height of the package and greatest at the ends of the latter, varies in discontinuous manner whilst matching the outer contour of the layer 2. There again,recourse is bad to elements 8 of variable dimensions to correspond to the variable thicknesses of the layer of material 4 along the axis XY of the package. The advantage of having varying thickness in the direction of the axis of the package resides in the fact that it enagles a gain in weight.

In fact, the radioactivity being less at the ends of the package, the layer of lead can be of less thickness, the thickness of the layer situtated between the lead and the outer shell being all the greater. Now, the density of this layer is distinctly less than that of lead.

Due to the characteristics which have just been described, the package according to the invention enables:

the ensuring simultaneously of the removal of the calories emitted by the radioactive material and the absorption of the neutrons which the latter emits;

the enabling of a simple construction;

enabling gains in weight;

control of the nuclear interaction in the case of multiple cavities;

increase in the thermal capacity in the neighbourhood of the cavity and the making of the temperatures along this cavity uniform.

In the case of the packages of FIGS. 3, 8 and 9, there are provided cooling crowns 14 arranged on the outer surface of the shell 3, these crowns being of course replaceable by any other type of fins or of pins.

In the embodiment of FIG. 10 and 11, the package according to the invention compriseson the one hand a layer of material 4 arranged gainst the outer surface of the shell 3 and combined with conducting elements 14a of the pin type, fixed on the shell 3 and projecting at the surface of the layer 4 and, on the other hand, a layer 15 of type of mortar or cement with a hydraulic binder base, arranged between the shell 3 and the layer of dense material 2.

The hydraulic binder layer 15 and which can enter in the constitution of the layer of material 4 is preferably of the aluminous type (ciment fondu").

Its chemical composition is advantageously as follows:

A1 0 35-40% CaO 35-40% Fe O l0-l 5% FeO 28% SiO 27% TiO O-3% Various O3% A composition which has given good results is as follows:

A1 0, 38% C210 3 8% Fe,0 12% FeO 5% SiO 4% TiO 2% Various 1% water/cement comprised between 0.35 and 0.45.

Thus, a meter cube of mortar can be constituted as follows:

Aluminous cement 700 kg WATER 280 l Granulate(comprising various fillers) 1000 I As regards the abovesaid granulate, its composition is advantageously as follows:

Particles between 0.5 and 1 mm of diameter 20% Particles between 1 and 2 mm of diameter 30% Particles between 2 and 5 mm of diameter 50% Fillers intended to increase the heat conductivity, constituted generally by metallic particles of steel or aluminium, or other conductive materials such as graphite or aluminium, may be incorporated in the layer 15.

To constitute the layer of material 4, there is used as granulate, materials with a high content of hydrogen and/or boron, of the type of those indicated above, and minerals such as colemanite (35 0 ZCaO, 5H O), pandermite (68 0 SCaO, 9H O), or again boric acid (H B0 To establish ideas, there is given herebelow an example of composition for the layer of material 4:

Aluminous cement 600 kg Water 220 kg Polyethylene (granules of about 3-5 mm) 600 kg Colemanite sand (05 to 2 mm) kg In the abovesaid composition, the colemanite sant is advantageously replaced by the powder with a granulometry of 50 to 500 micrometers.

As regards more particularly the abovesaid protective layer 15, it can be constituted in such a manner that it comprises zones of conductivity and of reduced mechanical strength, denoted by 15a, and situated at the level of the ends of the package, on both sides of the portion including the elements 14a, the zone corresponding to the portion provided with the said elements 14a being denoted by 15b and showing the characteristics indicated abovesuited to improving the thermal conductivity. It is indicated that the thickness of the zone 15b is generally of the order of 5 to 25 mm. Moreover, it is then advantageous to provide at the inner surface of the package a zone 15c, offering both a good thermal insulation and a good resistance to crushmg.

The zone l5a, includes advantageously insulating fillers such as expanded clay, globular alumina, vermiculite, perlite and expanded slag, which enagels it to play the role of a damper in the case of violent shock or dropping of the package.

The zones 15a, 15b and are obtained, in practice, by casting successively and in suitable order the corresponding constituent materials between the layer 2 and the outer shell 3.

It is noted that it is convenient to remove from the constituent mortar or cement of the layer 15 excess gas or free water which it contains and which could cause an excessive overpressure inside the shell 3. To do this, after several days of hardening, the temperature of the layer 15 is raised gradually to the maximum temperature of use whilst enabling excess steam or gas to escape from the shell 3.

Moreover, to avoid in the case of tire the risks of bursting of the shell 3, there is provided in the latter safety devices 17, constituted for example by fuses of metal or of a synthetic material such as a polyamide.

The thickness of the layer of material 4 can reach 20 cm or more. The thermal conductivity of this layer being relatively little raised as a result of the presence of neutron absorbing fillers, the dissipation of heat coming from the material contained in the package is ensured by means of elements 14a.

It is advantageous to provide fillets for necks at the base of the pins 14a to improve the adherence of the layer of material 4.

To facilitate possible decontamination operations of the package, there is provided according to the invention a coating of paint 18 covering both the layer 4 and the elements 14a and applied after evaporation of the major part of the free water from the mortar.

According to the preferred embodiment illustrated in FIG. 11, the package according to the invention comprises, on both sides of the portion including the cooling element, that is to say at its two ends, a continuous rim 19 of which the surface is substantially at the same level as the ends of the said cooling elements.

By means of these continuous rims, the cooling elements are less exposed to shock and it becomes possible to fix, by simple means such as straps 20, a removable jacket 21, metallic or of synthetic material possibly reinforced, covering portion which includes the cooling elements.

This construction enables further reduction, at the time of operations of loading or unloading the package, of the risks of contamination of the portion including the cooling elements.

To avoid risks of tearing at the time of operations of immersion in the pool, clean water is introduced into the espace arranged between the jacket 21 and the wall of the package, by resorting to a system of communicating vessels. This system of communicating vessels comrpises:

on one hand, a flexible inlet pipe 22 which is connected by a connector 23 to a pipe 23a enabling the water arriving through the pipe 22 to enter the space comprised between the jacket 21 and the wall of the case on, as shown,

on the other hand, a second flexible pipe 24 connected by a connector 25 to a pipe 26 passing through the continuous upper rim 19 andenabling the pressures to be balanced.

The ends of the pipes 22 and 24 remain fixed during handling with respect to the plane of the water and are arranged for example in the manner indicated in FIG. 11.

Due to this method of proceeding, any penetration of contaminated water inside the space comprised between the jacket 21 and the wall of the package is avoided.

It thus becomes possible to use, for constituting cooling elements, a carbon steel of good thermal conductivity, stainless steel being reserved for the members and surfaces which are not protected by the removable jacket.

As seen in FIG. 11, the cavity of the package is provided with a purging pipe 27 which opens at the level of zone 19.

lclaim: 1. Package for the storage and transportation of radioactive substances, said package having a composite wall comprising from inside to outside, an inner shell surrounding a cavity for containing said radioactive substances, a surrounding layer of dense material for protection against gamma radiations and an outer shell, said composite wall including a surrounding layer of neutron absorbing hydrogeneous material which constitutes an efficient neutron barrier for neutrons of high energy and heat-conducting elements traversing at least partially said neutron barrier and at least partially buried in said material sufficiently to conduct to the outside the heat produced therein.

2. Package according to claim 1, wherein said layer of neutron-absorbing material is arranged against the outer surface of the outer shell, said heat-conducting elements being of the type of fins or pins, fixed against said outer shell, and projecting at the surface of said layer.

3. Package according to claim 1, wherein said layer of neutron absorbing material is situated inside the outer shell and said heat-conductive elements, of which at least one end is free, are buried therein.

4. Package according to claim 2, wherein the heatconducting elements have a general radial direction.

5. Package according to claim 2, wherein the heatconducting elements have a general direction inclined with respect to the radius.

'6. Package according to claim 2, wherein the heatconducting elements are constituted by metallic blades fixed by welding on the outer shell of the package, parallel to the axis of the latter, said blades including on their free edge a succession of teeth folded by their sides at their blade support and having undergone twisting so that their flat portions are situated in successive planes substantially parallel between themselves and perpendicular to the axis of the package.

7. Package according to claim 3, wherein the heatconducting elements are metallic and have a section especially in a U or in an I, said elements being arranged so that the horizontal bar of the U or the vertical limb of the 1" are oriented radially.

8. Package according to claim 3, wherein the heatconducting elements are fixed by their ends against the corresponding constituent element of the wall of the package, the other end being curved with respect to the general direction of the element so as to be substantially parallel to the corresponding constitutent element, of the wall of the package.

9. Package according to claim 1, wherein the neutron absorbing hydrogeneous material is rich in boron.

10. Package according to claim 1, comprising a plurality of said cavities bounded by inner shells and distributed around its axis, the spaces comprised between the various inner shells being at least partially filled by a metallighter than lead.

11. Package according to claim 2, including a layer of material of the type of mortar or cement with a hydraulic binder base arranged between said outer shell and said layer of dense material.

ments, can be avoided. 

2. Package according to claim 1, wherein said layer of neutron-absorbing material is arranged against the outer surface of the outer shell, said heat-conducting elements being of the type of fins or pins, fIxed against said outer shell, and projecting at the surface of said layer.
 3. Package according to claim 1, wherein said layer of neutron absorbing material is situated inside the outer shell and said heat-conductive elements, of which at least one end is free, are buried therein.
 4. Package according to claim 2, wherein the heat-conducting elements have a general radial direction.
 5. Package according to claim 2, wherein the heat-conducting elements have a general direction inclined with respect to the radius.
 6. Package according to claim 2, wherein the heat-conducting elements are constituted by metallic blades fixed by welding on the outer shell of the package, parallel to the axis of the latter, said blades including on their free edge a succession of teeth folded by their sides at their blade support and having undergone twisting so that their flat portions are situated in successive planes substantially parallel between themselves and perpendicular to the axis of the package.
 7. Package according to claim 3, wherein the heat-conducting elements are metallic and have a section especially in a ''''U'''' or in an ''''I,'''' said elements being arranged so that the horizontal bar of the ''''U'''' or the vertical limb of the ''''I'''' are oriented radially.
 8. Package according to claim 3, wherein the heat-conducting elements are fixed by their ends against the corresponding constituent element of the wall of the package, the other end being curved with respect to the general direction of the element so as to be substantially parallel to the corresponding constitutent element, of the wall of the package.
 9. Package according to claim 1, wherein the neutron absorbing hydrogeneous material is rich in boron.
 10. Package according to claim 1, comprising a plurality of said cavities bounded by inner shells and distributed around its axis, the spaces comprised between the various inner shells being at least partially filled by a metal lighter than lead.
 11. Package according to claim 2, including a layer of material of the type of mortar or cement with a hydraulic binder base arranged between said outer shell and said layer of dense material.
 12. Package according to claim 11, wherein the hydraulic binder is of the aluminous type.
 13. Package according to claim 1, comprising a removable protective jacket, of which the two edges are fixed to continous rims which occur at the two ends of the package, the assembly being such that clean water can be circulated in the space arranged between said jacket and the wall of the package, whereby, on operations of immersion in a pool, contamination of the portion of the package comprising the cooling elements, can be avoided. 